You can check your Progress under Start - Inventory - Items.I have a lot of spoilers used here to provide a better overview, simply fold the spoiler from your currently needed.The clickable Timeline links will open in a new window and the video will start at the time or at the Item. In the Youtube Description you have the same Timeline too. Directly on Youtube dont open a new Window when you click a Timestamp. (Works only there)

I have created own Maps for each Collectibles. The Maps are cleared of any other Symbol (except Fast Travel). The Numbers on the Map match up with the Numbers in the Timeline. Warning, the maps are very large!